1. Field of the Invention
The present invention relates to radio communication antenna systems for wireless networks. More particularly, the invention is directed to active array antennas and related methods.
2. Description of the Prior Art and Related Background Information
Modern wireless antenna systems generally include a plurality of radiating elements that may be arranged over a ground plane defining a radiated (and received) signal beamwidth and azimuth angle. Antenna beamwidth has been conventionally defined by Half Power Beam Width (“HPBW”) of the azimuth or elevation beam relative to a bore sight of such antenna element.
Real world applications often call for an antenna radiating element with frequency bandwidth, pattern beamwidth and polarization requirements that may not be possible for conventional antenna radiating element designs to achieve due to overall mechanical constraints.
Currently, there is a demand for cellular base station antennas that produces 90 degree azimuth beamwidth at two separate frequency bands, i.e., 1.7 GHz-2.2 GHz and 700 MHz to 900 MHz. Conventional techniques to broaden the emission beamwidth include employing metallic and dielectric shrouds. These techniques are effective for broadening the beamwidth for high frequency bands (1.7 GHz-2.2 GHz); however, these techniques are either not effective or are difficult to implement at frequencies below 1 GHz. At lower frequencies (i.e., longer wavelength), the thickness of the dielectric shroud becomes impractically large to achieve the beam broadening effect. Moreover, simple thin-wall metallic shrouds becomes resonant, thus reducing the frequency bandwidth.
Accordingly, a need exists for an improved antenna element architecture which allows a dual-polarized dual-band broad beamwidth antenna.